Apparatus for the production of mesityl oxide



H. GUINOT June 6, 1933.

APPARATUS FOR THE PRODUCTION OF MESITYL OXIDE Filed July 23, 1930 M JMink Nut Patented June 6, 1933 PATENT OFFICE HENRI GUINOT, F MELLE(DEUx-SEV'BES), FRANCE APPARATUS FOR THE PRODUCTION OF MESITYL OXIDEApplication filed July 23,

alcohol.

It is well known that the present direct methods of making mesityl oxidefrom acetone do not give high yields. It is better to convert theacetone first into diacetone alcohol and then transfer the latter intomesityl oxide (Organic Syntheses, Roger Adams, editor-in-chief, JohnWiley & Sons, Inc., New York, 1921, volume I, pp. 45, 47, 53; 54).

. The conversion of diacetone alcohol into mesityl oxide may be effectedby adding a very small uantity of various reagents acting as dehy ratingcatalysts such as, for example, zinc chloride, concentrated phosphoricacid, concentrated sulphuric acid (Knoevenhagel Ger. Pat. No. 162,281 of1904), concentrated hydrochloric acid (Hoffman U. S. Pat. No. 1,474 035of 1922), iodine (Hibbert, J our. Amer. hem. Soc. 37 1915,

i 1755) and then distilling slowly. 1

In the employment of all of these processes there is always observed theformation of a certain quantity of undesirable condensation products,which is no doubt due to the fact that the concentration of the catalystin the reaction medium increases ver mark-. edly as the distillationprogresses. urthermore, in such processes the yield of mesityl oxide isproportionately less on account'of the formation of the relatively"large quantity of acetone due to thecdepolymerization of the diacetonealcohol (Organic Syntheses loc. cit.).

According to the present invention these disadvantages are overcome withthe result that nearly quantitative yields of pure mesi- 'tyl oxide areobtained.

The process which will be set forth in detail hereafter consistsessentially in carrying out the continuous decomposition of thediacetone alcohol by heating it to boiling point in the presence of aconsiderable excess of water containing a small quantity of cata-.

lyst.

The operation is carried out in a heated reaction vessel which issupplied continuously 1930. Serial No. 470,626.

with diacetone alcohol which is gradually converted into water andmesityl oxide. The latter compound forms with water a mixture of minimumboiling point, boiling at 91.5 C., and is rapidly eliminated from thezone 55 of reaction. In order that the azeotropio mixture can continueto be formed indefinitely, it is necessary that there should always besuflicient water in the reaction vessel, the water formed in thereaction being itself not sufficient to insure this condition. Themixture, water and mesityl oxide, is separated by a distillation systemwhose elements are conveniently combined in order to profit'from thefact that the mixture of minimum boiling point (or mixture of similarcomposition) can be separated into two constituents by decantation,while the'diacetone alcohol carried off with the vapors issuing from thereaction vessel is constantly refluxed back into the latter. Thewatermesityl oxide azeotropic mixture consists of 69% mesityl oxide and31% water. This mixture separates, on standing, into two layers-theupper one being mesityl' oxide 5 saturated with water, and the lower onebeing water containing less than 1% of mesityl oxide.

From the facts presented above it will be readily seen that on accountof the large proportion of water, which the mixture of minimum boilingpoint contains the water required to form the azeotropic' mixture wouldsoon be completely removed from the reaction vessel, thus leading to theprincipal faults of previous processes unless some provision is made to.supply additional water to the reaction v"mixture. According to thepresent invention, it is necessary to return to the reaction vessel theexcess water entrained by the azeotropic mixture in a manner so as. tomaintain always substantially constant the composition of the reactingmix ture. 3

It is the combination of these arrangements that permits the almostcomplete avoidance of the depolymerization of diacetone'alcohol intoacetonevand the production of highly condensed or resinous products.

In the accompanying drawing there is shown diagrammatically theapparatus of the invention.

Below will be cited an example of a preferred method of carrying out thepresent invention. It is distinctly understood, however, that theprocedure outlined is given merely as an illustration and that theinvention is in no way limited by the specific procedure specified, andthat it is desired to claim as within the scope of the invention theusual equivalents which would naturally occur to one skilled in the art.

Into a heated reaction vessel (1) there is placed:

Parts Diacetone alcohol 10 Water O Phosphoric acid (45 B.) '1

Upon heating the mixture to boiling, the diacetone alcohol is graduallytransformed into mesityl oxide which distills forming with the waterpresent a mixture of minimum bolling point, boiling at 91.5 (1., whichcontains 69.4 parts mesityl oxide.

The production of acetone is-insignificant, but as the diacetone alcoholemployed often contains a little of it, it is necessary to provide forits elimination.

For this purpose the Vapors issuing from the reaction vessel (1) aresent to the lower part of column (2), at the upper portion of which theyare condensed by the condenser (13). The'liquid resulting from thiscondensation is refluxed by the pipe (14) back to the upper part of thecolumn where the acetone gradually collects and -is drawn off by pipe(3) at a convenient rate.

The liquid flowing down to the bottom of the column (2) returns to thereaction vessel by pipe (4) carrying with it the diacetone alcohol whichmay have been entrained by the vapors issuing from the reaction vessel.

The binary mixture, ide, collects in the middle portion of the column,whence it is run oil into the decanter (6) after being cooled in thecoil. (5) immersed in the cooling tank (15 The liquid separates into twolayers the upper layer of which consists of mesityl oxide saturatedwith'water and is sent through pipe (7) to the top of the heated column(8).

he pure mesityl oxide flows out from the bottom of this column by pipe(9). At the top of this column there is obtained a mixture consisting ofwater and mesityl oxide, which is sent to the decanter (6) after passingthrough condenser (16).

The lower layer consisting of water saturated with mesityl oxide isdivided into two parts. One part corresponding to the water formed inthe reaction vessel is eliminated from the apparatus by pipe (10) it canbe treated in a continuous or discontinuous mannor for the recovery ofthe mesityl oxide; the

water and mesityl ox-- other part is refluxed by pipe (11).

The diacetone alcohol which leaves the reaction vessel in the form ofmesityl oxide is replaced at the same rate by fresh diacetone alcoholcoming from the supply tank (12). The reaction can be continued in thismanner indefinitely, the water and phosphoric acid in the reactionvessel always remaining in their original concentrations. Under theseconditions the yield of pure mesityl oxide rezllches approximately 96%of the theoretica If desired, boththe procedure and apparatus outlinedabove may be modified somewhat without departing from the scope of thepresent invention. For example, in the distillation portion of theprocess and apparatus the usual modifications of both ap paratus andmethod of operating used in other azeotropic processes such as used inthe dehydration of alcohols, acetic acid or other substances may beemployed. Furthermore, ifdesired, the separation of the mixture of.water and mesityl oxide may be carried out as an independent continuousor discontinuous operation.

In a general way the process is applicable also to the manufacture ofthe homologues of mesityl oxide.

Now having described my invention, what I desire to claim is:

1. In an apparatus for the continuous production of mesityl oxide fromdiacetone alcohol, the combination of a boiling vessel, a. column,'meansfor introducing the vapors from said boiling vessel into the bottom ofsaid column and means for returning the reflux from the bottom of saidcolumn to the said boiling vessel, a condenser, means for conducting thevapors leaving the top of the column through said condenser andmeans forreturning tothe top of the column at least a part of the condensate fromsaid condenser, means for withdrawing the azeotropic mixture of mesityloxide and water from an intermediate region of the column, means forcooling and separating said mixture into two layers, means for returningat least a part of the aqueous layer to the said boiling vessel, meansfor introducing the mesityl oxide layer into the to of a second column,heating means at the bottom of the said second column, means forwithdrawing vapor from the top of the said second column and means forwithdrawing substantially water-free mesityl oxide from the bottom ofthesaid second column.

2. In an apparatus for the continuous production of mesityl oxide fromdiacetone alcohol, the combination of a boiling vessel, a column, meansfor introducing the vapors from said boiling vessel into the bottom ofsaid column and means for returning the reflux from the bottom of saidcolumn to the to the reaction vessel said boiling vessel, a condenser,means for conducting the vapors leaving the to of the column throughsaid condenser an means for returning to the top of the column at rleast a part of the condensate from said condenser, means forwithdrawing the azeotropic mixture of mesityl oxide and water I from anintermediate region of the column, means for cooling and separating saidmixl0 ture'into two layers, means for returning at 7 least a part of theaqueous layer to the said boiling vessel, means for introducing themesityl oxide layer into the to of a second column, heatingmeans at theottom of the said second column, means for withdrawing vapor from thetop of the said second column, means for condensing said vapor, meansfor introducing said condensate into the said means for separating theaqueous and mesityl oxide layers and means for with-- .drawingsubstantially water-free mesityl oxide from the bottom of the saidsecond column.

' In testimony whereof I aflixmy signature.

HENRI GUINOT.

